The present invention relates to a light-sensitive mixture comprising a 1,2-naphthoquinone-2-diazide-sulfonic acid ester and a resinous binder which is insoluble in water and soluble or at least swellable in aqueous-alkaline solutions. The invention also relates to a reproduction material produced with this mixture.
Light-sensitive compounds based on 1,2-naphthoquinone-diazides are known from DE-C 938,233 corresponding to GB-B 739,654; U.S. Pat. No. 3,802,885; DE-A 3,100,077 corresponding to U.S. Pat. No. 4,424,270; and EP-A 0,052,788 corresponding to U.S. Pat. No. 4,407,926. These compounds are di- or trihydroxybenzophenones which are partially or completely esterified with 1,2-naphthoquinone-diazide-sulfonic acids. The compounds are mainly used as completely esterified representatives, i.e., they no longer contain any free phenolic hydroxyl groups. Compounds of this type have, however, the disadvantage of a light sensitivity which is too low for some purposes, or the disadvantage of inadequate solubility in the organic solvents normally used for coating supports such as printing plates. Moreover, in combination with binders such as novolaks, they give layers which, in the unexposed state, are not sufficiently resistant to the commonly used alkaline developer solutions. The layers are attacked to a certain extent during printing in offset printing presses when alcohol-containing fountain solutions are used and also by petroleum hydrocarbons such as are frequently used during printing for washing off the oleophilic printing ink from the plate.
DE-C 1,118,606, corresponding to GB-C 935,250, discloses 1,2-naphthoquinone-diazide-sulfonic acid esters of phenolic compounds such as derivatives of diphenylmethane. For reasons of adhesion, these esters contain at least one free hydroxyl group.